In recent years, the development of fuel cells has thrived due to a focus on saving energy and reducing emissions. Fuel cells can be classified into, for example, phosphoric acid, alkali, molten carbonate, solid oxide and polymer electrolyte (also known as PEFC) types, according to the type of electrolyte membranes they use. Of these, PEFC has such characteristics as being able to operate at low temperatures and having a high power output density, and its commercial application in uses such as a power source for automobiles, and in household co-generation systems is advancing.
Conventionally, the electrolytes (polymer electrolytes) used in PEFC have generally been electrolyte membranes (PFSA membranes) made from polyperfluorocarbon sulfonic acid (for example Nafion® made by DuPont). However, there are a number of problems with PFSA membranes, including those made from Nafion.
High manufacturing cost is one example. The perfluoro monomer used as the raw material is expensive, and it also seems that this high manufacturing cost is caused by the greater number of steps (procedures) required for polymer and film formation and the like processes, when compared to the process of manufacturing generic polymers. Thus, the proportion of the material cost of the entire fuel cell occupied by the cost of the electrolyte membrane is very large, and this is a large impediment to the popularization of fuel cells. At present, various measures are being carried out in respect of this problem, and there are advancements in the development of lower cost polymer electrolyte membranes in which the principal component is hydrocarbon. However, it is very difficult to manufacture low cost polymer electrolyte membranes that have an equivalent ionic conductivity and durability to PFSA membranes such as Nafion, and these have not led to a fundamental solution.